The ink-jet recording method is a recording method of forming ink images on a recording material by directing jets of ink drops at the recording material by the use of various techniques. This recording method enables high-speed and full-color printing to be easily achieved with a low noise level. In recent years, therefore, the utilization of ink-jet recording methods has been spreading at a rapid rate. According to such a method, fine drops of ink are jetted from nozzles at a high speed so as to direct toward a recording material. And a large quantity of solvent is contained in the ink used. As a result, recording materials for ink-jet recording are required to absorb ink promptly.
The recent years have also seen rapid proliferation of personal computers and digital cameras. Under these circumstances, image qualities on a level similar to those attained by silver salt photography have come to be required for images printed from digital image information. In other words, it has become necessary that, in printing images of digital information origin, recording materials can ensure high-density colors, high resolution and excellent color reproduction in the prints obtained.
In full color recording, ink-jet printers using the so-called dye ink rank as the dominant printers. This is because the dye ink generally comprises at least three kinds of ink prepared by dissolving dyes of different colors in separate portions of a solvent respectively and the dyes comprised therein as coloring ingredients are superior in point of color formation. On the other hand, ink-jet printers using the so-called pigment ink are employed for specific purposes alone under the current circumstances. The pigment ink used therein comprises at least three kinds of ink, wherein pigments of at least three different colors are dispersed as their respective main coloring ingredients and water is used as their respective main dispersion media. The purposes for using them center chiefly on the printing of rough images, e.g., wide-format images including poster. This is because the images printed in pigment ink are inferior in color reproduction though they have excellent light resistance and water resistance.
In general, ink-jet recording materials designed placing importance on ink absorption are provided with an ink-receiving layer having minute pores for promoting penetration of ink. When pigment ink is used in recording on a recording material designed for dye-ink use, it sometimes occurs that pigment particles stop up the foregoing minute pores. In this case, ink absorption becomes bad, and pigments as coloring ingredients are confined within a very thin surface region of the ink-receiving layer. As a result, the rubbing resistance of recorded images deteriorates.
On the other hand, when the pores present in an ink-receiving layer are greater in size than pigment particles, the pigments as coloring ingredients penetrate too deeply in the ink-receiving layer. As a result, the images recorded are inferior in color density and color reproduction. As matters stand, therefore, no recording materials capable of delivering both excellent color reproduction and high ink absorption when pigment ink is used are known yet.
As an answer to such a problem, Japanese Tokkai Hei 10-119417 (the term “Tokkai” as used herein means an “unexamined published patent application”) proposes providing a layer which can swell in ink by containing a water-soluble resin on an ink penetration layer containing an inorganic filler. However, such an ink absorption layer is slow in ink drying speed, and so it has an image formation problem.
Further, Japanese Tokkai Hei 11-254818 discloses the recording sheet provided with an ink-receiving layer containing silica grains. However, such a sheet has insufficient color reproduction.